Method for producing 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane

Abstract

The invention provides a process for production of high purity 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (BPTMC) which comprises: (a) a reaction step wherein phenol is reacted with 3,3,5-trimethylcyclohexanone (TMC) in a slurry containing phenol adduct crystals of BPTMC in the presence of an acid catalyst; (b) a neutralization step wherein after the reaction, the resulting reaction mixture in the form of slurry is neutralized with an alkali while heating to convert the slurry to a solution; (c) a primary crystallization and filtration step wherein the resulting solution is cooled and the resulting phenol adduct crystals of BPTMC are collected by filtration; (d) a secondary crystallization and filtration step wherein the adduct crystals obtained in the primary crystallization and filtration step are heated in a crystallization solvent to dissolve the crystals therein to prepare a solution and then the solution is cooled to crystallize BPTMC out of the solution, followed by collecting the crystals of BPTMC by filtration; (e) a filtrate recycling step wherein at least a part of the secondary crystallization filtrate obtained in the secondary crystallization and filtration step is returned to the reaction step. The process provides uncolored high purity BPTMC in high selectivity and in high yield in an industrially stable manner which is substantially free from residual phenol and trace impurities such as sodium, chlorine and sulfur and hence which is suitable for use as raw materials for the production of resins for optical use.

What is claimed is:  
     
       1. A process for production of high purity 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane which comprises: 
       (a) a reaction step wherein phenol is reacted with 3,3,5-trimethylcyclohexanone in a slurry containing phenol adduct crystals of 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane in the presence of an acid catalyst;  
       (b) a neutralization step wherein after the reaction, the resulting reaction mixture in the form of slurry is neutralized with an alkali to a pH of 5 to 8 while it is heated so that it is converted to a solution;  
       (c) a primary crystallization and filtration step wherein the resulting solution is cooled and the resulting phenol adduct crystals of 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane are collected by filtration;  
       (d) a secondary crystallization and filtration step wherein the adduct crystals obtained in the primary crystallization and filtration step are heated in a crystallization solvent to dissolve the adduct crystals therein to prepare a solution and then the solution is cooled to crystallize the 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane out of the solution, followed by collecting the crystals by filtration;  
       (e) a filtrate recycling step wherein at least a part of the secondary crystallization filtrate obtained in the secondary crystallization and filtration step is returned to the reaction step.  
     
     
       2. The process as claimed in  claim 1  wherein phenol and 3,3,5-trimethylcyclohexanone are used in a phenol/3,3,5-trimethylcyclohexanone molar ratio of 4 to 9 in the reaction step. 
     
     
       3. The process as claimed in  claim 1  wherein the reaction is carried out at a temperature in the range of 15° C. to 40° C. in the reaction step. 
     
     
       4. The process as claimed in  claim 1  wherein the acid catalyst is hydrogen chloride gas.